//* dummy aliens that move only in ortogonal direction

alien_dummy_images = new Images('dummy',3);

function AlienDummy() {
  // contructor
  var that = new Alien();
  that.images = alien_dummy_images;
  that.shrapnel = 0;
  
  // dummies move only 1 ortogonal direction
  that.randomize = function() {
    switch (Math.round(Math.random()*4)%4) {
      case 0: this.dx = +this.max_speed; break; 
      case 1: this.dx = -this.max_speed; break; 
      case 2: this.dy = +this.max_speed; break; 
      case 3: this.dy = -this.max_speed; break; 
    }
  }
  that.randomize();

  // update dummy
  that.update = function() {
    // move dummy
    this.simpleMove();
    // keep dummies near earth
    this.constraint(300);
  }
 
  return that;
}

function AlienDummies(ACount) {
  // create array of dummy aliens
  var that = new Array();
  for (var i=0; i<ACount; i++)
      that.push(new AlienDummy());
  return that;  
}
